Wiped Film Distillation: Why Terpene Stripping Makes or Breaks Your Distillate Purity

Terpene stripping is a critical step in wiped film distillation. If not done right, it can significantly impact your final product’s purity. Why is terpene stripping so crucial? Heavy terpenes act as major contaminants. They can reduce THC levels from 98-99% to 88-90%. And these heavy terpenes could be a reason your distillate isn’t reaching its full potential.

Many distillers easily remove light and medium-weight terpenes during the first pass. However, the heavy terpenes remain, negatively impacting distillate purity. This is especially true in wiped film distillation, where the short residence time doesn’t visibly discolor the terpenes, masking the problem.

Recognizing a Proper Terpene Strip

So, how can you tell if you’ve effectively removed those heavy terpenes? There are two tests: the sticky test, which can be a bit informal, or you can do an HPLC test for more accuracy. The key is to extract a measurable amount of cannabinoids during your terpene pass.

The Sticky Test and HPLC Verification

So, what is the “sticky test”? The “sticky test” involves observing the texture of the distilled terpenes. As your terpenes are distilling, grab a small sample between your index finger and your thumb. An oily feel might indicate up to 10% cannabinoids. The presence of a short, thin string suggests about 20%. (For a better visual, watch this video https://www.instagram.com/reel/C2ayjwxSFLP/?utm_source=ig_web_copy_link&igsh=MzRlODBiNWFlZA==)

As practical as the “sticky test” might seem, it’s not always reliable. An HPLC test is much more accurate. It measures the cannabinoid content in about 20-40 minutes, but can be a costly solution since the equipment is expensive.

Targeting Light, Medium, and Heavy Terpenes

Light terpenes, with only five carbons, evaporate at close to room temperature. Medium-weight terpenes (10 carbons) boil off easily at under 100 degrees Celsius. The problem lies with heavy terpenes.

These heavier terpenes only evaporate just before the cannabinoids. To ensure their removal, it’s essential to push the temperature high enough. This ensures even those stubborn compounds make their way out. Remember, the light and medium terpenes are easy to remove; the heavy terpenes require a more deliberate approach.

Cannabinoids as a Metric

Why intentionally remove a few cannabinoids? It serves as a reliable marker. It confirms that all terpenes, including the heavy ones, have been distilled. While it seems counterintuitive, losing a small, measured amount of cannabinoids ensures a cleaner final product.

Typically, crude oil contains around 5% terpenes. If you lose 20% of that 5% as cannabinoids during terpene stripping, you’re only losing 1% of your total cannabinoid content. This minimal loss results in a yield of approximately 99%. With an additional 2-3% lost to residue, the trade-off is worth it for the increase in purity.

Optimizing Temperature, Vacuum, and Feed Rate

Starting Parameters

A good starting point is an evaporator temperature of 155 degrees Celsius. Maintain a vacuum level better than 200 millitor. If your vacuum exceeds 300 millitor during terpene stripping, troubleshoot. Your system is either compromised or the decarboxylation process was insufficient.

Proper decarboxylation is crucial. Wiped film distillation won’t fix under-decarbed material. Running it through again will only worsen the vacuum.

Multiple Passes and Terpene Preservation

What do you do with the terpenes collected during the first pass? In many cases, they get tossed. But for operators looking to preserve terpenes for reintroduction or to create a full-spectrum profile, it’s worth taking a closer look.

Ethanol-extracted terpenes tend to be lower in quality. That’s because the lightest terpenes—those with just five carbon atoms—often evaporate along with the ethanol. These highly volatile compounds are essential for a complete flavor profile. Without them, the final product can smell muted or off.

Wiped film systems can recover terpenes, but what you get depends heavily on the quality of your starting material. Poor-quality biomass often yields terpenes with strong off-notes—like horseradish or fish. But with high-quality input and the right parameters, wiped film can help recover the heavier, more robust compounds.

Still, if your goal is to preserve a more complete terpene spectrum, solventless methods or light hydrocarbon extractions (like butane or propane) are generally better. These processes do a much better job of retaining the delicate aromatics that define a strain’s unique scent and flavor.

Cold Traps and Flavor Preservation

If you’re serious about preserving flavor, a well-optimized cold trap is essential. Wiped film systems can strip terpenes effectively, but without a cold trap, much of that value is lost.

For best results, use a cold trap chilled to -100°C or lower. Dry ice can get you close, but ultra-low mechanical traps do a better job of capturing even the most volatile terpenes. When combined with the medium and heavy terpene fractions collected during distillation, this gives you a more complete and accurate flavor profile.

If flavor is your goal, consider running a very light first pass. This helps capture the most volatile compounds—the “flavor fraction.” These lighter terpenes have strong aromas. The heavier ones, by contrast, tend to contribute less to the smell and more to contamination in your final distillate.

Final Thoughts

Mastering terpene stripping is about understanding the interplay of various factors. Temperature, pressure, flow rate, and composition all play a crucial role. There is no single magical setting. Instead, a flexible, observant approach is needed. This ensures you achieve the desired purity and terpene profile. By balancing these elements and continually measuring your output, you can transform your distillation process and achieve superior results.